Recently, in accordance with the storage capacity increase of a disk array system, importance thereof in a data processing system has been increasing more and more. Therefore, in order to ensure reliability of user data in a disk array system, it is important to write data correctly in the required location according to a data input or output request given from a host such as a data processing unit and to detect incorrect data when the data read out in accordance with a request are incorrect.
Techniques for ensuring data reliability in a disk array system include a method in which a redundant code (check code) is added to the data which are to be stored in a storage device such as HDD (hard disk drive), and the addressing correctness in the data access is verified by the use of the added redundant code when the data is read.
An HDD compatible with conventional SCSI (Small Computer System Interface) or Fibre Channel (FC) employs a method in which the sector length thereof is extended and the redundant code is recorded in the extended part.
Also, in a specification of the U.S. Patent Application Laid-Open No. 2003/0135577, a disk array system employing ATA (AT Attachment) is described. ATA is of a type in which the sector length thereof is fixed and cannot be extended.